Filter system



Sept. 4, 1951 R. L. RATHMANN FILTER SYSTEM 2 Sheets-Sheet 1 Filed June 21, 1948 Y\ Q. a.

' IN V EN TOR. 'Ro BERT L .RATH MAN N W M ATTORNEYS p 4, 1951 R. RATHMANN ,633

FILTER SYSTEM Filed June 21, 1948 2 Shets-Sheet 2 INVENTOR. Reamer LKRATHMANN ATTORNEYS Patented Sept. 4, 1951 UNITED STATES PATENT OFFICE FILTER SYSTEM Robert L. Rathmann, Tranquillity, Calif,

Application June 21, 1948, Serial No. 34,292

3 Claims.

My invention relates to an oil filter system for hydraulic apparatus and is more specifically concerned with an attachment to be added to standard or well-known oil circulating systems for con trolling heavy equipment, which makes possible the addition of a standard oil filter.

In many heavy road building equipment, earth moving devices, and agricultural implements, earth engaging means thereof are manipulated by hydraulic control systems employing hydraulic cylinders or rams extended or contracted in response to hydraulic pressures imposed thereon. Such control systems are inherently expensive in initial cost and have been found to deteriorate rapidly because of dust, dirt, and other abrasive material that accumulate in the hydraulic system and are circulated with the fluid. Much of the abrasive material has been found to come from elements of the control systems themselves, such as metal chips from the ram, valve, pump or other structure. The extent of the wear in conventional systems in normal operation necessitate a complete overhaul annually. The repetitious nature of the overhauling and repairing operations is so great that in many instances the expense of maintenance of such hydraulic control systems far overshadows the even considerable expense of its initial purchase.

It is conventional in hydraulic control systems to employ a fluid reservoir, a pump, and a valve in association with one or more rams Whereby fluid pressure generated by the pump may be selectively imposed on opposite ends of the ram or rams. When a ram is manipulated, fluid is bled, from the end of said ram opposite the end to which fluid pressure is applied, back through the valve and from the valve to the reservoir. In order that the system may at all times be ready to operate, the pump is run constantly. When a ram is maintained in predetermined position, the valve seals the ram from the rest of the control system and fluid from the pump is by-passed through the valve back to the reservoir, the pump merely serving to circulate the fluid to the reservoir and to remain ready for immediate efiect on the ram in response to valve manipulation. At such times, the pump is said to be in stand-by condition. When in stand-by condition, the valve effectively isolates both ends of the ram from the control system and maintains the ram inpredetermined position. It is significant that during normal operations hydraulic control systems are maintained in stand-by condition approximately 95% of the time.

An obvious solution to the problem of maintenance previously discussed is that of filtering the fluid to remove all abrasive material there'- from. For many years eiforts have been expended by manufacturers of hydraulic control systems and others to this end but without success. It has been found impractical to build filters to withstand the excessive pressures in hydraulic control systems and still capable of effec'- tive operation in screening abrasive material from the hydraulic fluid. The experimentation in this direction has been so extensive and the lack of success so universal, that the manufacturers of hydraulic control systems have generally reached the conclusion that there is no possible solution to the problem and that periodic repair and replacement is unavoidably a concomitant defect of such systems. The filtering system of the present invention has succeeded in solving the problem and has proved itself by extensive use capable of reducing maintenance expenses 'almost to the point of elimination.

It is an object of the present invention to minimize wear and maintenance expenses incident to operation of hydraulic control systems.

Another object of my inventionis to provide a fluid filtering system whereby standard oil filters can be employed in hydraulic control systems without danger of rupture because of excessive pressures. I

It is another object of my invention to provide a means for by-passing excessive pressures around a filter so that it will be impossible for excessive pressure to be built-up in the filter.

Another object is to provide a filtering system for hydraulic control systems in which a pressure pump, while in stand-by condition, is employed to circulate fluid in the control system through the filtering system.

Another object is to provide, in an hydraulic control system in which a constantly running pump imparts circulatory movement to fluid in the System and a valve is manipulated periodically to impress part or all of fluid pressure generated by the pump upon a ram and to by-pass the fluid not directed to the ram back to the intake of the pump under substantially no pressure, a filtering system receiving said by-passed fluid and screening dirt, abrasive material, and other foreign matter therefrom.

Another object is to provide in an hydraulic control system having a fluid reservoir and a fluid pump which when in stand-by condition circulates fluid from the reservoir, through the pump, and back to the reservoir, a valve interposed the pump and the reservoir adapted to resist flow of tional valve HI. cat-e with the interior of the valve l4 and also fluid from the pump to the reservoir sufliciently to divert such flow through a filter, and adapted to open for passage of fluid directly from the pump to the reservoir upon the exerting thereon of a pressure in excess of a predetermined magnitude.

It is also among the objects of my inventionto provide a simple attachment which can be applied to standard oil pressure systems for operating heavy equipment which will permit the use of a filter, thereby prolonging the effective life of the equipment and reducing the cost of expen sive repairs.

Other and further objects and advantages of my invention will become apparent from the drawings and the specifications relative thereto.

In the drawings:

Fig. 1 shows a portion of a conventional hydraulic control system to which the system of the present invention has been added.

Fig. 2 is a cross-section taken on line 2-2 of Fig. 1 of means provided by the present invention against which fluid pumps employed in hydraulic control systems build up sufficient pressure for filtering purposes when the pump is operating in a stand-by condition.

Fig. 3 is a fragmentary sectional View taken on line 3--3 of Fig. 2.

Fig. 4 is a schematic diagram il ustrating the operation of the system of the present invention in combination with a conventional hydraulic control system.

' Fi 5 is a schematic diagram s milar to that of t e present invention.

Fig. 6 is a fragmentar view of the system shown in Figs. 4 and 5 illustrating the control valve in an intermediate position in which the part a flow of h draulic fluid is directed through the fil ering syst m.

Fi 7 is a sch mat c diagram illustrating the fluid flow in a modified form of the present invention.

'In t e drawin s. Fi 1 i lustrates a well-known hydrau c s stem which com rises a fl id reservoi tank Ill. having an outlet conduit communicatin with a pum I2. and a pump disc arge co du t |3 communicating wi h a direc- Conduits l5 and i5 communiwith an h draulic iston or ram. su sefluentlv to be de cribd. to be o erated bv the flu d p essure. Further details of the internal connec ions will be ome a arent in an ex anation o Fi 4. The ta k is p v ded with a fill ng o ening closed by a can I! having a breathing openin I8 therethrou h. The o ening permits ex ansion and cont action of fluid in the tank incident to tem- "perature varia ions and the like and precludes the subiecting of the tank to damaging pressure variations.

Th directional valve I4 is also formed with a mounting flange I9 ada ted to mount the valve ;to the tank In. The flange H) is formed with a ram bleeding bore 20 and a by-pass bore 2| adapted to communicate with the interior of the valve M. The significance of bores 20 and 2| will also become apparent in the subsequent dis- 4 up mechanism, designated generally 30, which comprises a cylindrical housing 3| defining a chamber 32, as seen in Fig. 2. The upper portion of the housing 3| is internally threaded, as at 33, and a plug or cap 34 is threadedly disposed therein. The plug 34 is formed with an axial bore 35 adapted to receive a valve stem 36. The purpose of the back pressure valve is to provide a closure against which the pump l2 may build up small pressures suflicient for filtering purposes and which opens at predetermined pressures to avoid all excesive pressures of damaging efiect on a filter subsequently described.

Whereas, I=have herein illustrated the means for closing the top of the housing 3| as a; plug,

such as 34, it will become apparent that the principal function of such member is to position the stem 36 and to act as a backing for a compression spring 31. Any member which will perform this function should be considered an equivalent. Other devices which could be substituted might include a plate welded to the top of the housing 3| and could be either solid or could assume the form of a spider bracket.

The lower extremity of the housing 3| is formed with a plurality of perforated sections 49, shown in Figs. 2 and 3, which, as will be seen, act as oil passages when the pressure build-up mechanism 30 functions to relieve pressure. A valve 4| is slideably disposed in the chamber 32 and is attached to the stem 36 by means of a threaded connection 42. The spring 31 is adapted to press against the top of the valve 4| urging it in a downward direction in fluid-tight engagement against a plate 43 interpositioned the housing 3| and the flange IS. The plate 43 is formed with a bore 44 adapted to register with the bore 2| for the passage of oil or other hydraulic fluid and is interposed the flange l9 and the tank ill on which the plate 43 is also formed with a bore 50 adapted to communicate with the bore 44 and having an interiorly threaded section 5| adapted to receive a tubular fitting 52. A conduit 53 is secured in communication with the bore 50 by means of the fitting 52 and communicates with a filter 54. The filter 54 is of more or less standard construction and is provided with a discharge 55 which communicates with the discharge line H from the oil tank by means of a conduit 56. A bore 5! is formed through the plate 43 in fluid communication with the ram bleeding bore 20 and the interior of the tank Ill. The plate is conveniently mounted on the tank by bolts 58 extended upwardly through the flange I9, passed through the plate and screw-threadedly engaged to the tank I0. By extending the plate upwardly. as at 59, along an end of the tank, a convenient mounting for the filter 54 is provided.

Reference to Figs. 4, 5 and 6 will clarify the system of the present invention. It is to be understood that the illustrations of the valves It in the above figures are purely schematic to indicate the operation thereof and are not in;

tended to duplicate the exact structure employed. The valve includes a body Na in which a core Mb is rotatably positioned. The body provides a high pressure inlet I40 connected by the conduit l3 to the high pressure side of the pump l2. The housing further provides a pluralit of outlets Md, Me and M), respectively, connected to one end of a cylinder 60, to the by-pass bore 2| and to the opposite end of the cylinder 60, respectively. The core has formed therein a passageway my having an enlarged intake end in constant registration with the inlet I40 and selectively registering at the opposite end thereof with a control outlet [401, Me or IM or with any adjacent two thereof. The housing further provides bleeding openings M72 and I42 in fluid com munication with the control openings Md and ldf, respectively, by way of conduits I6 and I5, respectively. An opening I ia is provided in the housing intermediate th bleeding openings Ida" and. Mh and is in fluid communication with the bleeding bore 2G, previously described. A passage I470 is positioned so that as fluid is fed to one end of the cylinder 60 fluid is bled from the opposite end of the cylinder back through the passage Mk into the tank ID. A piston 6| is slidably mounted in the cylinder 59 and the piston and cylinder together constitute a two-way control rain of well-known form.

As shown in Fig. 4, when pressure is employed at the control opening Md its respective bleeding opening Mh is closed. shown in Fig. 5, when the hydraulic control in stand-by condition. the pump urges fluid through the passage Mg which is maintained in registration with the opening Me and fluid circulated through the bypass bore 2|. In such condition the core l lh blocks control openings Idd and i4) and bleeding openings Mi and l lh.

In Fig. 6 an intermediate condition is illustrated in which a portion of hydraulic fluid from the pump is directed through the passageway Idg out of the opening Me and back to the by-pass bore 2| and the remainder of the fluid through the opening M to the cylinder 6d to control the piston 6|. It will be noticed that in this condition the opening Mh is in partial registration with the passage We permitting the opposite end of the cylinder gradually to bleed. For purposes of convenience, the bleeding bore 253 and the by-pass bore 2| are schematically illustrated intubular form in Figs. 4, 5 and 6.

As will be readily understood, the spring 3? (referring to Fig. 2) will determine the amount of pressure against the bottom of the valve ii, which will cause the valve 6| to lift from sealing engagement with the plate 53, thereby permitting fluid to escape from the passageway M through the apertures 6 and into the tank l0. Screw- .threaded adjustment of the plug 34 in the housin 3| predetermines pressure exerted by the spring 3! downwardly and the pressure the pump I2 may build up against the bottom of the valve 4| for filtering purposes.

Operation The operation of the device is clearl apparent and is briefly summarized at this point. The pump at i2 is motivated from a power take-off of a traofior or the like, not shown, in order to circulate hydraulic fluid from the tank so through the conduit ll, pump l2, discharge conduit 3, valve M, and back to the tank through the bleeding bore and/or the by-pass bore 2|.

The valve core Mb of the valve I4 is most frequently positioned as shown in Fig. 5 for stand-by operation of the pump, in which position the total discharge of hydraulic fluid from the pump is directed through the outlet Me and the by-pass bore 2| to the pressure build-up mechanism 3B. When the valve is so positioned, the piston 6| of the cylinder 69 i locked in predetermined position by the effective sealing of the control outlets Md and I4 and the bleeding openings Hi and Ih by the core Idb. In this stand-by condition, the pump builds up a sufficient pressure against the mechanism 30 to force fluid through the filter 54 and back through the conduits 56 and I to the intake side of the pump I27. This pressure is quite low being generally of the magnitude of five pound to the square inch, or less. Under normal stand-by conditions the entire volume of hydraulic fluid pumped through the pump I2 is filtered at 54 and effectively cleaned of dirt, rust, scale and other abrasive material.

In the event excessive pressure is built up against the filter 54, incident to clogging or the like, the valve 4| is urged upwardly against the resistance of the spring 3'! and the hydraulic fluid circulated through the tank as is normally done by pumps in stand-by condition in conventional hydraulic systems. .It will be perfectly obvious that the tank II! can be under no pres-.- sure because of the breather opening I8 and thus the pressure to which the filter 54 is subjected is accurately controlled by the pressure buildup mechanism 30. Attention is again directed to the fact that in hydraulic control ystems the valve l4 and pump l2 are operated in stand-by condition for normally in excess of 95% of the time of operation of the control system.

When it is desired to move the piston 6| of the cylinder 60 to the left, as viewed in Fig. 4, the valve core Mb is rotated counter-clockwise from the stand-by position of Fig. 5 to direct hydraulic fluid from the pump to the right end of the cylinder by way of conduit l6. Simultaneously the bleeding opening I42 is connected in fluid communication with the bore 20 through the opening Ma and the left side of the cylinder permitted to bleed back to the tank l0 through the conduit I5. So positioned, the opening M71. is closed by the core a is the control opening I41 and the stand-by opening Me. When the piston in the cylinder is moved, pressures many times that to which a normal filter may be exposed are required. For example, such filters are constructed to withstand and operate effectively under pressures of four or five pounds per square inch. The pressures required to manipulate the ram may approximate fifty times this pressure. Thus when the ram is manipulated, the sealing of the opening Me by the core Mb protects the filter against all uch pressures. These periods during which the filter is divorced from the control system seldom exceed from two to four percent of the operating time of the control system.

It will be evident that in the operation of the control system there will be times at which the passage Hg is directed to a pair of the adjacent openings Md, Me and M). This condition is shown in Fig. 6 and is employed when it is desired slowly to move the piston 6| in either direction. In Fig. 6 the passage |4g is in registration with both of the openings Me and Mi. The partial registration constricts the fluid flow through both of the openings. Under such condition a partial flow of fluid through conduit l5 serves to position the piston and the remainder of the fluid is diverted through the bore 2| and the filter 54, the pressure build up mechanism 30 serving to resist fluid flow through the bore 2| sufliciently to divert the same through the filter. As before, the pressure build up mechanism 3|] operates as a relief valve in the event that excessive pressures are imposed thereon and dissipates said pressure into the tank ID. Simultaneously the opening |4h i arranged in constricted fluid communication with the bore 20 permitting the end of the cylinder toward which the piston BI is moved to bleed back through the bore 20 to the tank [0. The total time during which the valve [4 is employed in the con-- dition shown in Fig. 6 rarely exceeds from one to three percent of the total operating time of the system.

The filtering system of the present invention is convenient to install, easily accessible for repair,

and is accurately adjustable by mean of the nut 34 to impress predetermined pressures on the filter of small magnitude. This accurate control permits the employment of low pressure filters and makes available their effective operation and economy of construction. The filtering system is efiicient in that hydraulic fluid is diverted through the filter after it ha passed through the hydraulic control system and in that it is normally operative for approximately 95% of the time the control system is in operation. In actual operation the system and elements of the present invention have reduced repair and maintenance expenses for hydraulic control systems with which they have been employed almost to the point of elimination.

Modified form The hydraulic system schematically shown in Fig. 7 employs elements already described and like parts are given like numbers. A valve 19, however, is employed differing from the valve I l previously described. In the system shown in Fig. 7, the bore 26 is the only path for fluid from the valve to the tank in and thus returns all hydraulic fluid to the tank resulting irom bleeding of the cylinder 68 or from the positioning of the valve in stand-by condition. The valve 1E3 employs a two-way structure having an inlet ii and discharge ports E2, 13 and "M. A centrally disposed core i is formed with the passageways l6 and il. As shown in the schematic illustration, the passageway ll communicates between the ports II and I2 and the passageway i6 between the ports 73 and M so that the flow of fluid is as follows: Commencing with the pump I 2, fluid is forced under pressure through the line [3, passageway TI, conduit [6 and into the cylinder 68 forcing the piston 6| to the left. Fluid which is held in the cylinder to the left of the piston BI, is forced through the line l5, passageway l6,

and bore 23 to the tank I9. Ihe bore 26 is provided with a. pressure build-up mechanism 33 in the manner already described for bore 2i. It will be readily understood that when the valve is positioned in a stand-by condition there will be a flow of hydraulic fluid from the pump to the tank. The pressure build-up mechanism 30 resists such flow sufliciently to create a pressure suificient to divert the hydraulic fluid through the conduit 53, filter 54 and conduit 56 back to the conduit H and thence to the pump I2. Under such condition, the total flow of hydraulic fluid is filtered.

When the valve H3 is positioned as shown in Fig. 7, controilably to position the piston 6| in the cylinder 6i], it will be apparent that no greater pressure is imposed on the bore 28 than the weight of fluid standing thereabove and the resistance ofiered by the pressure build-up mechanism 3Q. Said mechanism diverts the hydraulic fluid through the filter 54 as previously described and opens whenever pressure due to clogging or periodic fluid surges exceeds the structural limits of the filter 54 and for dissipationv of such excessive pressure in the tank. The system of the present invention operates similarly when' the valve 10 is positioned to change the pattern of fluid flow to the cylinder or directly back to the tank for stand-by operation.

Thus, it will be seen that I have provided a pressure relief system or attachment to be used in connection with standard hydraulic systems, which permits the use of filtering devices which will substantially clean the hydraulic fluid used in the system, thereby preventing excessive wear on the pump and the hydraulic control pistons.

While I have herein shown and described my invention in what I have conceived to be the most practical and preferred embodiments, it is recognized that departures may be made therefrom within the scope of my invention, which is not to be limited to the details disclosed herein, but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices.

This application is a continuation in part of my application having Serial Number 788,026, which was filed November 25, 1947, resulting in Patent Number 2526,411 dated October 17, 1950.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a hydraulic control system having a reservoir, a pump, and a two-Way ram; the combination of a conduit interconnecting the reservoir and the pump; a valve in fluid communication with the pump; said valve having a bypass port, a pair of pressure su ply ports, a pair of blee ing ports, and an exhaust port in fluid communication with the reservoir; a conduit interconn cting one end of the two-way ram and a pressure supply port and a bleeding port; a conduit interconnecting the opposite end of the ram and the other'supply port and bleeding port; a conduit interconnecting the by-pass port and the reservoir: a pressure build up valve conne ted to said last named conduit precluding fluid flow therefrom into the reservoir when pressure in said conduit is less than a pr determined magnitude and opening for discharge into the reservoir when the pressure exceeds the predetermined magnitude; and a filter in fluid communication b tween said last named conduit and the conduit interconnecting the reservoir and the pump; the valve having a controllably positioned core adapted to direct fluid therethrough from the pump to the by-pass port and to block the bypass port while directing fluid flow to an individual pressure supply port while simultaneously blocking the bleeding port to which the supply port is connected by the conduit and the I opposite pressure supply port and directing return fluid flow therethrough from the opposite bleeding port to the exhaust port.

2. In a hydraulic control system including a two-way hydraulic control ram, and a pump having an intake and a discharge; a control valve having an inlet, a pair of pressure outlets, a pair of bleeding openings, a discharge opening, and a core positionable to connect the inlet to either of the pressure outlets while closing the remaining outlet and a bleeding opening and simultaneously connecting the remaining bleeding opening to the discharge opening, said core also having an intermediate position in which both pressure outlets and both bleeding openings are closed and the inlet connected to the discharge opening; bleeding conduit means connected between the intake of the pump and the discharge opening of the valve; by-pass conduit means connected between the intake of the pump and the discharge opening of the valve in parallel relation to the bleeding conduit means; a pressure release valve in the by-pass conduit means; a filter in the bleeding conduit means; and conduits individually connecting the discharge openings of the valve and opposite ends of the ram and bleeding openings of the valve with opposite ends of the ram.

3. In a hydraulic control system including a double acting hydraulic control line, and a pump having an intake and a discharge; a control valve having an inlet connected to the discharge of the pump, a pair of alternately openable pressure outlets connected to opposite ends of the ram, a pair of alternately closeable bleeding openings connected to opposite ends of the ram and a discharge opening connected to-the intake of the pump, said valve being operable selectively to direct hydraulic fluid under pressure from the pump to selected ends of the ram While bleeding the opposite end of the ram back through 10 the valve discharge opening and into the intake on the pump; a filter connected between the discharge opening of the valve and the intake of the pump; and a by-pass conduit having a pressure release valve therein connected between the discharge opening of the valve and the intake of the pump in parallel relation to the filter.

ROBERT L. RATHMANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,020,774 Nilson Mar. 19, 1912 1,346,086 Funk July 6, 1920 1,379,259 Hans May 24, 1921 2,242,807 Austin May 20, 1941 2,335,231 Armington et al. Nov. 30, 1943 

